Ergonomic handle for hand-held tools

ABSTRACT

Disclosed is an ergonomic handle for a hand-held tool, in particular for an air tool. The handle has a trilobular shape, designed to provide a secure grip and thereby reduce operator fatigue. The handle is also flared at the end which sits nearest the workpiece. This flared feature allows the operator who presses downward on the handle while operating the tool to avoid having his hand slip past the end of the sleeve. The handle is not an integral part of the tool and can be removed to allow maintenance, repair or replacement of the tool. Moreover, in a preferred embodiment, the handle has a bore along its axis and is provided with a unique locking mechanism which prevents rotational or axial movement of the tool relative to the handle. Optionally, the outer surface of the handle is finished so as to reduce slippage in the event it becomes slick with perspiration or oil, and is made of a thermal insulating material to make use comfortable.

This is a divisional continuation of co-pending application Ser. No.07/393,835 filed on 8/14/89 which is a divisional of application No.07/258,236, filed 10/14/88, abandoned.

FIELD OF THE INVENTION

The invention relates to an ergonomically designed handle for ahand-held tool, particularly for an air tool, which reduces operatormuscle fatigue.

BACKGROUND OF THE INVENTION

In a manufacturing facility engaged in mass production, air tools areoften used on the assembly line. In operating an air tool over thecourse of a typical shift, a worker encounters substantial stresses andstrains on muscles and ligaments of the hand and arm. This isparticularly true for a rotating air tool, such as a screwdriver, aboltdriver, a nut socket, or a drill, which must be gripped tightly toresist both reaction torque of the tool and to provide the axial forcenecessary to insure tool engagement.

The stresses and strains increase worker fatigue. This can result in aloss of efficiency or a reduction in product quality. Worker injury canalso result, which can lead to loss of work time and a need for areplacement worker, worker's compensation claims, and sometimes evenliability for the employer.

The science of ergonomics or human engineering has attempted to answermany of the problems facing today's assembly line workers. Among theproblems which have been confronted are those facing a worker operatinga rotating tool. Deprag (Tradename) offers a air-powered screwdriverwith what is described as an "ergonomic" handle. In cross-section, thishandle has four lobes. More specifically, it has four slightly arcuatesides of substantially equal length, with rounded corners, so as to formone lobe at each corner.

The Deprag handle, however, is not truly ergonomic. The four lobeddesign does not closely fit a gripped hand, and the handle is somewhatdifficult to grip over the course of an entire shift. In addition, thehandle is an integral part of the tool, and cannot be removed. Thus, ifthe plastic grip is damaged or not desirable to a particular operator,there are no alternatives but to replace the relatively expensive motorhousing/grip or force the operator to use a tool which is damaged or notcomfortable to him.

It is clear that what is needed is a handle which is truly ergonomic, inthe sense that muscle and ligament strain and fatigue is minimized. Sucha handle should also be readily detachable so that the grip can bereplaced or the tool can be operated without it, if desired by theoperator.

SUMMARY OF THE INVENTION

The invention relates to an ergonomic grip handle for a hand-held tool,in particular for an air tool. The handle is designed to provide asecure grip, which reduces operator fatigue, and so that the operator'shand will not slip axially towards the work piece.

In cross-section, the handle has three arcuate sides of substantiallyequal length all of which are joined so as to form one lobe at each ofthree rounded corners This trilobular shape conforms to the shape of ahuman hand held in the gripping position, with one lobe of the handleseating in each pocket in the hand. This allows the handle to besecurely gripped.

This trilobular shape also provides a mechanical lock which reduces thegrip effort required to resist the reaction torque of the tool. With thecommon cylindrical tool housing, this reaction torque is resisted merelyby the friction between the operator's hand and the tool outsidesurface. This friction force is a function of the coefficient offriction between his skin and the tool housing material and grip force.The trilobular shape augments this friction force by providing amechanical lock force, thereby reducing the grip effort required.

The handle is also flared at the end which is designed to be nearest theworkpiece. This feature allows the operator who presses downward on thehandle while operating the tool to avoid having his hand slip past theend of the handle.

The handle is preferably not an integral part of the tool and can beremoved to allow maintenance, repair or replacement of the tool.Moreover, in a preferred embodiment described below, the handle isdesigned as a sleeve which fits over the tool, the sleeve being providedwith a unique locking mechanism which prevents rotational or axialmovement of the tool relative to the sleeve.

Preferably, the outer surface of the handle is finished so as to reduceslippage in the event it becomes coated with perspiration or oil, and isalso made of a thermally insulating material which protects the worker'shand against heat or cold. Appearance is also improved by this texture.These and other advantages and features of the invention are more fullydescribed below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an assembled clutch housing andmotor housing, with an ergonomic sleeve of the invention in place.

FIG. 2 is a sectional view of the ergonomic sleeve of FIG. 1.

FIG. 3 is cross sectional view of the ergonomic sleeve of the invention,taken at line 3--3 of FIG. 1.

FIG. 4 is a partially cut away view of the clutch housing of FIG. 1.

FIG. 5 is a partially cut away view of the motor housing of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the ergonomic handle of this invention isillustrated in FIG. 1, where the handle is in the form of a tubularsleeve 10, having a cylindrical bore 18. Bore 18 is sized to tightlyaccommodate an assembled motor housing 12 and clutch housing 14. Incross-section, the outer surface of sleeve 10 has three arcuate sides 13joined together by rounded corners 11 to form a trilobularcross-section. See FIG. 3. The distance between the middle of eacharcuate side of the handle and the opposing corner is preferably fromabout 3 centimeters to about 4 centimeters, and more preferably is about3.5 centimeters. These dimensions, together with the trilobular shape ofsleeve 10, provide a secure and comfortable grip for a worker's hand.

The outer surface of sleeve 10 is flared outwardly at an end 16, to atleast about 1.0 centimeter larger, side to corner, than the main body ofthe sleeve. The flared section, in combination with the secure gripprovided by the trilobular shape of sleeve 10, helps provide substantialresistance to axial movement of a worker's hand gripping sleeve 10 inthe direction of flared end 16.

A typical operating assembly designed for use with sleeve 10 has a motorhousing 12 which is substantially cylindrical and includes an air motorto drive a tool as well as gears to provide the desired torque for thetool. A clutch housing 14 attaches to motor housing 12 and includes aclutch assembly to provide a driving connection between the motor andthe tool.

In order to closely accommodate the clutch assembly, clutch housing 14includes three cylindrical sections each with a smaller diameter thanthe adjacent section. The section with the smallest diameter is locatedat the end of clutch housing 14 furthest from motor housing 12 andclosest to the tool itself.

The tool (not shown) extends from the end of clutch housing 14 and isdriven through the clutch assembly. The tool may, for example be arotating tool such as a screwdriver, a nut driver, or a drill. Sleeve 10could also be used with a non-rotating tool, such as a rivet-driver.Alternatively, a handle having the ergonomic shape of sleeve 10 could beused on a conventional tool which is not air-powered, such as a manualpowered screwdriver.

A preferred clutch assembly for use in the invention can be adjusted toimpart a specified torque to the nut, bolt, or screw being driven.Typically, the clutch can be adjusted to automatically stop rotation ofthe tool when the workpiece is torqued a specified amount. The clutchmay also start rotation of the tool automatically, upon downwardpressure on the tool by the operator.

A preferred assembly for locking sleeve 10 in place on assembledhousings 12 and 14, so that sleeve 10 is prevented from relativerotational and axial movement, is shown in FIG. 1. The preferred lockingassembly relies upon the interaction of male tabs and female tabs, or"flats," as described below.

As shown in FIG. 5, the outer surface of motor housing 12 is providedwith two female tabs 22 and 24, one on either side thereof. As seen inFIGS. 1 and 2, located on the inner surface of sleeve 10 are male tabs26 and 28. These two sets of tabs are mated during assembly of thehousings and sleeve 10.

To accomplish mating, motor housing 12 is inserted into bore 18 from theend of sleeve 10 opposite flared end 16. Motor housing 12 is thenrotated so as to align tabs 22 and 24 with tabs 26 and 28, and pushedinwardly to lock it into place inside sleeve 10.

Clutch housing 14 is next inserted into bore 18 from flared end 16, andis threaded to motor housing 12 via threads 30 and 32 (shown in FIGS. 4and 5) to form joint 20. If the tool is primarily rotating clockwise,i.e., if used for inserting a right-hand threaded bolt, then the threadsat joint 20 should be left-handed. When the threads at joint 20 areopposite to the direction of tool rotation, then rotation will forcemotor housing 12 and clutch housing 14 together, rather than apart,during operation.

As shown in FIG. 1, the lip of clutch housing 14 nearest joint 20 abutsthe ends of male tabs 26 and 28 and thereby prevents axial movement ofsleeve 10. The locking provided at the sides of the two sets of tabsprevents rotation of sleeve 10 about housings 12 and 14.

Sleeve 10 can also be fitted on a hand-held air tool which is actuatedby a lever which extends substantially parallel to, but slightlyupwardly from, the length of motor housing 12. Installing sleeve 10 onsuch a tool is carried out as described above, with the sole differencebeing that the lever should not sit directly above one of the trilobularedges formed by corners 11 of sleeve 10. Sleeve 10 should instead bealigned so that the lever is above one of its three sides 13.

As noted above, the distal sections of clutch housing 14 have a smallerdiameter than the section nearest joint 20. However, a number ofvariations of the diameter of the clutch housing, and its varioussections, as well as of the motor housing 12 are possible. The onlyrequirement is that with the tabular locking system shown, the diameterof the sections of motor housing 12 and clutch housing 14 which arenearest tabs 22 and 24 must be approximately the size of bore 18 inorder to lock the two sets of tabs and prevent relative movement ofsleeve 10.

Generally, sleeve 10 must be constructed of a relatively rigid material.If the material is readily deformable, male tabs 26 and 28 could betwisted completely out of locking position by the reaction torquebetween sleeve 10 and housings 12 and 14 occurring when sleeve 10 isgripped tightly to resist the rotation of the tool. In the preferredembodiment, sleeve 10 is constructed of Fiberglass (TM) reinforcednylon; however, any of a number of materials with sufficient rigiditycan also be used.

The above-described locking system is advantageous because it is simplein design, relatively inexpensive to manufacture, and makes installationand removal of sleeve 10 relatively easy. To remove sleeve 10, in theevent that any portion of the tool needs repair, maintenance orreplacement, one simply unthreads clutch housing 14 and motor housing 12and pulls them apart Sleeve 10 can be re-used elsewhere after removal,or replaced onto assembled housings 12 and 14 as described above. Theact of removal does not destroy or in any way impair sleeve 10.

Although the aforementioned locking system has several advantages, anumber of other locking systems can be used with the invention. Theprimary requirement is that the system selected provide a secure lockbetween sleeve 10 and assembled housings 12 and 14. In addition,variations of the locking system described above can be made. Forexample, the location, number, shape and position of the tabs can bechanged.

A typical rotating air-powered tool used with sleeve 10 is intended foruse by a worker on an assembly line. Such a tool has a valve head (notshown) which is threaded to motor housing 12 by means of threads 34. SeeFIG. 5. An air hose (not shown) is threaded to the opposite end of thevalve head The air hose provides access for the compressed air whichdrives the motor in motor housing 12.

Typically, the tool hangs above a worker, suspended by the elasticaction of the coiled air hose, by a cable attached to the valve head, orby some other means. When the worker is ready to use the tool, he/shereaches up and grabs the tool by sleeve 10 and pulls it down. Afterfinishing the task, the worker releases sleeve 10 to allow the tool tobe pulled up and out of the way.

The worker must be able to grab the tool and quickly get it in positionfor performing the work at hand if he is to keep pace on the assemblyline. However, it is difficult to work quickly if the tool becomes slickwith oil or perspiration. Air-powered tools can easily become coatedwith oil, as it is typically injected from into the air line tolubricate the air motor Perspiration, of course, emanates from theworker, who may not have time to wipe his brow or the palms of his handswhile the assembly line is moving. Oil (or perspiration) reduces thecoefficient of friction between the operator's skin and the tool.

To overcome these problems, sleeve 10 can be provided with an anti-slipcoating. In a preferred embodiment, sleeve 10 has a mat finish, which isonly slightly abrasive. A more abrasive finish could be an irritant tothe hands over the course of a typical shift. The mat finish is alsomore pleasing in appearance than a more abrasive finish.

Another design consideration is that sleeve 10 should be a good thermalinsulator. When operating an air tool the air inlet end often becomesvery cold, due to the expansion of compressed air within the valve headand motor housing 12. Conversely, the end nearest to clutch housing 14becomes warm, due to the friction generated while doing work. A goodinsulator, such as the Fiberglass (TM) reinforced nylon of the preferredembodiment shields the operator's hand from these extremes and providesgreater comfort.

Sleeve 10 is preferably slightly longer than the width of a typicalworker's palm. This allows sleeve 10, and thus the tool to which it isattached, to be grabbed quickly near the middle and still be in positionto be used. If the sleeve was substantially longer than a worker's palmwidth it could easily be grabbed in a position in which the worker'shand would be too far from the tool to allow proper operation.Alternatively, if sleeve 10 were shorter than the palm width, the palmwould extend over the ends and operation would be difficult anduncomfortable.

As noted above, in cross-section the non-flared portion of sleeve 10preferably is about 3.5 cm from side to corner. Though this sizeprovides a comfortable grip for most people, it can be varied ifoperators with larger or smaller hands are using the sleeve.

It should be understood that the terms and expressions used above aredescriptive only and that the embodiments described are exemplary only.Accordingly, the scope of the invention is not to be limited by theforegoing terms and expressions but is defined only by the claims whichfollow and includes all equivalents, known and unknown, of the claimedsubject matter.

What is claimed is:
 1. In a rotational air tool having a substantiallycylindrical motor housing and clutch housing which are joined with athreaded joint, as well as a sleeve with a substantially cylindricalbore designed to accommodate the housings, wherein the improvementcomprises:said sleeve being locked to said housings by a pair ofradially inwardly extending male tabs on the inner bore of the sleevewhich lockingly mate with a pair of oppositely extending female tabs onthe outer surface of said housings, to prevent rotational and axialmovement of the sleeve relative to the housings; the outer surface ofsaid sleeve having a trilobular cross-section, and being ofsubstantially the same diameter over the majority of its axial length;and at least one end portion of said outer surface of said sleeve beingflared radially outwardly along the axial length of the handle andwherein the flared end portion has a trilobular cross-sectional shape.2. The device of claim 1, wherein the inner diameter of the sleeve issubstantially the same along its entire length.
 3. The device of claim1, wherein the outer surface has a mildly abrasive finish.
 4. The deviceof claim 1, wherein the sleeve is at least as long as the width of anoperator's palm.
 5. A tool and handle combination comprising:a tool bodyformed of first and second coaxial cylindrical members having abuttingends held together by mating threads; a recess in the cylindricalsurface of one abutting end, said recess being closed in one axialdirection by a shoulder on one member and in the other axial directionby a shoulder on the other member; a handle having a cylindrical boreadapted to receive said body members; and an inwardly extending tab insaid bore proportioned to substantially fill said recess both axiallyand circumferentially, so as to prevent significant relative motion ofsaid handle on said tool body.